Mozilla/5.0 (X11; Linux i686; rv:33.0) Gecko/20100101 Firefox/33.0 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0 Build ID: 20140902214533 The Sponsored Tiles pop-up close button is a little bit misplaced. STR: 1. Open Firefox using a clean profile. 2. Go to about:newtab. 3. Click on the "Sponsored" button located beyond each of the Sponsored Tiles. Expected results: The pop-up message is properly displayed inside the tile. Actual results: The close button (X) is a few pixels higher that it should be and it has a small underline beneath it. Notes: This issue does not reproduce on Mac OS X 10.9.4 Also reproduces on Latest Nightly and on Latest Aurora builds. Zooming the page in/out will make it disappear. It's only visible on 100% page zoom.